Heretofore apparatus for concentrating and collecting solar energy generally have consisted of lenses, reflectors and absorbers as separate components which are geometrically and mechanically positioned to form a solar collector with, for example, high concentration ratios and/or low thermal losses. This separation of collector components as typified by U.S. Pat. Nos. 4,058,110, 4,068,474 and 4,069,812, results in relatively deep thick structure and adds to the cost of making solar collectors. These collectors are also provided with tracking equipments needed for mechanically following the angular motions of the sun, which tracking mechanisms add substantially to the cost of collecting solar energy.
In order to obtain a relatively high concentration of radiant solar energy without tracking motions, which concentration is desirable to increase operating temperatures and to reduce the area of the absorber portions of solar collectors, wide-angle optics is necessary. U.S. Pat. No. 4,171,695 and U.S. Pat. No. 4,002,499 provide technology for non-tracking solar collectors with moderate concentration ratios. However, these collectors are thick requiring considerable depth for individual collectors and panels of these collectors. Thin collectors without external insulation making up thin panels offer great cost and space savings. Also the prior art cited describes collectors with elevation angle coverage divided equally about the normal to the aperture plane of the collector. This symmetry restricts the orientation of the collectors for full coverage to tilts with the vertical of approximately equal to the latitude angle of the location of the collector. It is often advantageous to mount collectors on vertical walls of buildings and still obtain the 60.degree. elevation angle coverage needed for tracking annular angular motion of the sun. Even though vertical wall installations result in smaller average projected area of the collector wall mountings are easier to keep free of snow and dirt and eliminate cutting holes in roofs.
The extraction of heat from solar absorbers is generally accomplished by circulating liquids or gases through them. These techniques for removing the heat collected often suffer from leaks, corrosion, freezing, poor heat transfer from absorber to circulant and the added cost of pumping circulant through the collector absorbers.
It is well known that solar collector lenses may focus and concentrate solar energy well in one plane, say the elevation plane, defined from a point on the horizon to the zenith, while the azimuth plane focusing may deteriorate badly during the early morning and late evening hours. Furthermore, optical losses are increased as lens' thickness is increased or the number of reflections on lens or reflector surfaces is increased.
Therefore, there is a need for a non-tracking solar collector that concentrates the sun's radiant energy over the wide elevation and azimuth angular interval traversed daily and annually by the sun with a collecting structure that is very thin, that can be wall or roof mounted, and that extracts heat efficiently without absorber circulants. The new collector described below has these and other beneficial characteristics. Furthermore, being easy to construct by miniaturized extrusion fabrication and having no external portions to position, additional cost advantages are realized with internal absorber solar collectors.